The 2001 LS6 MAFS is the same unit that is used in the 99 and up trucks. The 01-05 LS1's also use the same MAFS.
The 2002-2003 LS6 MAFS is just a 2001 LS6/LM7/LR8/8.1 MAFS with the screen removed. In 2004 GM put the screens back in the MAFS.

There is an aftermarket idler pulley relocation bracket, and then he would have to cut down the neck on the water pump to clear the TB. It's been done on the cable TB trucks and barely clears, but to my knowledge, no one has done it on a drive by wire TB, which is quite a bit larger. It may not clear even with cutting down the water pump neck. The only choice he may have is to run car accessories. The air filter and piping will have to be custom made, and he may have to run e-fans to avoid fan shroud interference.